Vehicles of a type using gasoline engine as a drive source are mainly available; however, vehicles of a type using an electric motor as a drive source are required at locations where occurrence of exhaust gas must be avoided. A motor-driven vehicle, however, has an inconvenience in the increased body weight and the shortened running distance. To cope with such an inconvenience, it has been increasingly required to develop a hybrid type vehicle including an electric motor in addition to an engine.
For example, Japanese Patent Laid-open No. HEI-8-175477 discloses a hybrid type motorcycle entitled "DEVICE FOR SWITCHING ENGINE POWER TO/FROM MOTOR POWER IN MOTORCYCLE OR THE LIKE".
As shown in FIG. 2 of the above document, although a piston and a cylinder are disposed along the center of a rear wheel 37 in the width direction of the vehicular body, main parts such as a transmission case 12 and a belt type transmission are disposed on the left side (as seen from a passenger) with respect to the center of the rear wheel 37, and further a motor 22 shown in FIG. 3 of the above document is disposed at a position largely shifted leftward from the center of the rear wheel.
That is to say, in the related art power unit, it is expected to take a lateral weight balance thereof.